The wings fold closely round the body of the insect, the right forewing completely enwrapping all but the basal portion of its fellow, and they are longer than the abdomen, projecting, when at rest, beyond its apex. Forewing longer than hind, six times as long as broad, and bright green in colour; hindwing twice as long as broad, and of a more delicate texture and colour than the forewing; anal area large, forming an unbroken contour with the rest of the wing. It folds fanwise against the body.
The wings are large and cumbersome, with no coupling apparatus; flight is slow, and only short distances are covered in one flight. The wing venation is very unstable, that of two specimens differing, whilst even the wings of one side of a single individual will differ from those of the other. The greatest variation has been noticed in the branching of Rs. The cross-veins are extremely variable. Certain features, however, are constant.
The Forewing (Pl. 41, Fig. 39).
The forewing exhibits a primitive venation and shows less clearly the two sources of tracheation, the costo-radial and cubito-anal; Sc is concave and is distally forked into Sc1 and Sc2, the latter of which dips down to run along or fuse with R1 for a short distance before curving outwards to the wing margin. C is absent, but Sc sends off a number, usually three, of cross-veins across the costal space to the anterior margin. Posteriorly the humeral veinlet comes off near the base of the wing; there is always a large space between this veinlet and the first veinlet across the costal space. About halfway along its length R, a convex vein, forks into R1, a straight, unbranched vein running to the wing margin terminating just in front of the apex, and into the Rs, which near its distal extremity bifurcates into R2 + 3 and R4 + 5. The former again branches into R2 and R3.
M, a convex vein, is fused basally with R for a short distance and is still in the primitively branched condition. Distally it bifurcates into M1 + 2 and M2 + 4. Cu is a straight vein arising from the cubito-anal trachea, but divides distally into Cu1 and Cu2, the former of which is convex and has a variable number of accessory veins, usually about three. Cu2 is a straight, unbranched, concave, weak vein lying in the anal furrow. 1A and 2A are both straight; the former is unbranched, whilst the latter divides into two. Crossveins are present, irregularly placed on all parts of the wing, but are more strongly developed between M and Cu, and between Cu1 and Cu2. The humeral veinlet is constant in position; there are always sub-costal veinlets present.
The Hindwing (Pl. 41, Fig. 39).
As in the forewing, C is absent, Sc is concave and two-branched; it gives off a variable number of costal veinlets and the humeral; there is always a large space between the former and the latter. Basally R and M are fused, this vein bifurcating to give two branches R1 and Rs + M; the former is a straight vein running directly to the margin in front of the apex. Rs + M forks giving Rs and M. This switching of Rs over to M is a constant feature and quite characteristic of the Plecoptera. Rs again divides into R2 and 3 and R4 + 5, but again may be three-branched, R2 + 3 splitting into R2 and R3. M is two branched into M1 + 2, M3 + 4, and is convex. Cu is two-branched, Cu1. having no accessory veins, whilst Cu2 is a very weak vein lying in the anal furrow. 1A is straight and unbranched. The anal area is increased by the development of accessory veins on 2A and 3A, while there is an indication of the formation of intercalary veins. Cross-veins are present throughout the wing membrane, but, as in the forewing, are irregularly placed, although more numerous than in the latter. Two strong sets strengthening the wings are developed between M and Cu, and between Cu1 and Cu2. The humeral veinlet is constant in position, and there are always sub-costal veinlets developed.